The long-range goals of the proposed research are to further our understanding of the mechanisms underlying the auditory processing of time-varying stimuli, and to determine how those mechanisms are affected by sensorineural hearing loss. There are three separate but related lines of research, and all focus to some extent on the potential role of peripheral compression in temporal processing. The influence of compression is evaluated by studying the effects of temporary, aspirin- induced hearing loss, permanent hearing loss, and model simulations. The first line of research focuses on the detection of brief signals as a function of prior masker stimulation. The underlying mechanisms could play an important role in enhancing newly arriving or intermittent signals, especially those in an on-going background. The general goal of this line of research is to test the hypothesis that the mechanisms underlying the temporal effect with off frequency tonal maskers differ from those underlying the effect with broadband noise maskers. The second line of research concentrates on phase effects in simultaneous masking, particularly on how the resulting temporal fluctuations influence the amount of masking. The general goal of this research is to gain a better understanding of the within- and across-channel mechanisms underlying these phase effects. This research should enhance our understanding of how the auditory system processes the temporal fluctuations inherent in many complex sounds, including speech, and could ultimately provide insight into why individuals with a sensorineural hearing loss have particular difficulties understanding speech in temporally complex backgrounds. The third line of research focuses on a recently described change in response growth from compressive to linear at high levels. This change, inferred from growth-of-masking functions, is responsible for a measured decline in temporal processing at high stimulus levels. The primary goal of this line of research is to gain a better understanding of the processing underlying this change in response growth.